K2JS: fix KT-5639 Exception in kotlin-js when directory is given instead of output file

#KT-5639 Fixed

compiler/cli/src/org/jetbrains/jet/cli/js/K2JSCompiler.java

@@ -143,6 +143,13 @@ public class K2JSCompiler extends CLICompiler<K2JSCompilerArguments> {
 
         OutputFileCollection outputFiles = translate(mainCallParameters, config, sourcesFiles, outputFile, outputPrefixFile, outputPostfixFile);
 
+        if (outputFile.isDirectory()) {
+            messageCollector.report(CompilerMessageSeverity.ERROR,
+                                    "Cannot open output file '" + outputFile.getPath() + "': is a directory",
+                                    CompilerMessageLocation.NO_LOCATION);
+            return ExitCode.COMPILATION_ERROR;
+        }
+
         File outputDir = outputFile.getParentFile();
         if (outputDir == null) {
             outputDir = outputFile.getAbsoluteFile().getParentFile();

compiler/testData/cli/js/outputIsDirectory.args

@@ -0,0 +1,4 @@
+$TESTDATA_DIR$/simple2js.kt
+-no-stdlib
+-output
+$TESTDATA_DIR$

compiler/testData/cli/js/outputIsDirectory.out

@@ -0,0 +1,2 @@
+ERROR: Cannot open output file 'compiler/testData/cli/js': is a directory
+COMPILATION_ERROR

compiler/tests/org/jetbrains/jet/cli/KotlincExecutableTestGenerated.java

@@ -174,6 +174,12 @@ public class KotlincExecutableTestGenerated extends AbstractKotlincExecutableTes
             doJsTest(fileName);
         }
 
+        @TestMetadata("outputIsDirectory.args")
+        public void testOutputIsDirectory() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/cli/js/outputIsDirectory.args");
+            doJsTest(fileName);
+        }
+
         @TestMetadata("outputPostfixFileNotFound.args")
         public void testOutputPostfixFileNotFound() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("compiler/testData/cli/js/outputPostfixFileNotFound.args");

compiler/tests/org/jetbrains/jet/cli/js/K2JsCliTest.java

@@ -30,18 +30,25 @@ public class K2JsCliTest extends CliBaseTest {
         Assert.assertTrue(new File(tmpdir.getTmpDir(), "out.js").isFile());
     }
 
+    @Test
+    public void outputIsDirectory() throws Exception {
+        executeCompilerCompareOutputJS();
+
+        Assert.assertFalse(new File(tmpdir.getTmpDir(), "out.js").exists());
+    }
+
     @Test
     public void outputPrefixFileNotFound() throws Exception {
         executeCompilerCompareOutputJS();
 
-        Assert.assertFalse(new File(tmpdir.getTmpDir(), "out.js").isFile());
+        Assert.assertFalse(new File(tmpdir.getTmpDir(), "out.js").exists());
     }
 
     @Test
     public void outputPostfixFileNotFound() throws Exception {
         executeCompilerCompareOutputJS();
 
-        Assert.assertFalse(new File(tmpdir.getTmpDir(), "out.js").isFile());
+        Assert.assertFalse(new File(tmpdir.getTmpDir(), "out.js").exists());
     }
 
     @Test